Up to half of the recent warming in Greenland and surrounding areas may be due to climate variations that originate in the tropical Pacific and are not connected with the overall warming of the planet. Still, at least half the warming remains attributable to global warming caused by rising carbon dioxide emissions.

Changes in the speed that ice travels in more than 200 outlet glaciers indicates that Greenland’s contribution to rising sea level in the 21st century might be significantly less than the upper limits some scientists thought possible, a new study shows.

In a pair of companion papers in Science Express this week, scientists investigate the role of surface meltwater on accelerating the flow of the Greenland Ice Sheet and outlet glaciers and conclude that, while surface melt plays a substantial role in ice sheet dynamics, it may not produce large instabilities.